1. Field of the Invention
The subject of the present invention is a safety device for electric openers of a vehicle, for example window lifters and sunroofs, this opener comprising a toothed wheel driven by a worm of a motorized reduction gear and a kinematic chain for linking between the wheel and the movable member to be driven (window or sunroof).
2. Description of the Related Art
As is known, three types of window lifter are currently used on motor vehicles:
a) arm and toothed sector window lifter: the output pinion of the drive motorized reduction gear rotates a toothed sector about a spindle which is fixed with respect to the door, and an arm secured to the sector transmits the movement to the window. PA1 b) rack cable window lifter: the output pinion of the drive motorized reduction gear directly drives the rack cable which slides in a sheath (metal or plastic). At the other end of the cable is fixed a carriage, sliding in the sheath, onto which the window is fixed. PA1 c) twisted cable (Bowden cable) window lifter: the output of the motorized reduction gear drives a drum on which there is wound a Bowden cable, which transmits the movement to a carriage sliding on a guide rail, this carriage being fixed to the window. PA1 a tooth inside the toothed wheel made in a recess of the latter, PA1 a pawl articulated on a rotary plate coaxial with the said toothed wheel about a spindle parallel to that of the latter, and one end of which interacts with the said tooth inside the toothed wheel in order to drive the plate in rotation when the toothed wheel rotates, PA1 a prestressed elastic member bearing on the plate and interacting with the pawl on the other hand, in order to keep the end of the latter bearing against the tooth inside the wheel for as long as the force transmitted by the latter remains below the predetermined value, this elastic member being capable of tilting into a second stable position in which it uncouples the pawl from the associated tooth when the force transmitted by the latter to the pawl exceeds the said predetermined value.
When an obstacle is located on the closure path of the window, the system must recognize the presence of an abnormal phenomenon and, if the force on the window exceeds a limiting value, the window must not continue its journey but must stop and at least release the force. This release of the force may be obtained either by releasing the window which descends under a small force or under the effect of its own weight if the friction in the lateral seal allows it, or by reversing the movement of the window which is then forced to descend.
In order to solve this problem electronic or electromechanical devices have already been produced which include sensors of various types capable of detecting the decelerations of the motor compared to the variations in voltage, or variations in current drawn, as well as the number of revolutions performed which they memorize, and which constitutes an image of the position of the window.
However, these electronic and electromechanical devices exhibit, amongst other drawbacks, the drawback of being relatively costly, due to their complexity, which is obviously an obstacle to their distribution on a wide scale. In addition, these mechanisms develop friction or use elastic drive components which do not make it possible to obtain reliable triggering as concerns the value of the force, and as concerns the sudden nature of the triggering.